Pressure-starting motor control device



AUI 18 1953 K. D. BURRELL ETAL 2,649,552

PRESSURE-STARTING MOTOR CONTROL DEVICE Filed July 11, 1950 e AL f a 2 fig-1 e] 6 3]- I 923 a f' 27 27 i l I6 IN VEN TORS D/CHARD C LA TJ olv BY ENNETHDBuR/PELL 77Zf'7mazqmmz f 9m/:dam /4 TTOR/VE YS Patented Aug. 18, 1953 UNITED PRESSURE-STARTING MOTOR CONTROL DEVICE Kenneth D. Burrell and Richard C. Latson, Zephyrhills, Fla.

Application July 11, 1950, Serial No. 173,026

(Cl. 31o-.68).

1 Claim. 1

rIhis invention relates to motor-driven hand tools, and more particularly to an electricallydriven hand tool suitable for bufng, polishing, sanding, and the like.

A main object of the invention is to provide a novel and improved motor-driven hand tool Which operates responsive to pressure exerted on the tool element thereof, the hand tool being deenergized when no pressure is exerted on its tool element, the device being very simple in construction, being easy to operate, and providing a saving in electric power.

A further object of the invention is to provide an improved electrically-driven hand tool of the type employed in sanding, polishing, buinng, and similar operations, said tool being inexpensive to manufacture, being sturdy in construction, involving relatively few parts, and being easy to take apart for servicing or for replacement of the tool element thereof.

Further objects and advantages of the invention will become apparent from the following description and claim, and from the accompanying drawings, wherein:

Figure l is a longitudinal, cross-sectional view taken through an improved electrically-driven hand tool constructed in accordance with the present invention;

Figure 2 is an enlarged, cross-sectional, detail view taken on line 2--2 of Figure 1.

Referring to the drawings, I I designates a housing adapted to be held by the user, and I2 designates an electric motor xedly secured inside the housing by any suitable means, not shown. The shaft of the motor is designated at I3, one end of said shaft being rotatably journaled in a suitable bearing I4 provided in the end wall of housing II, the opposite end portion of the shaft being rotatably supported in a bearing I5 mounted in a transverse partition wall I 6 -provided in the housing I I. Rigidly secured on the shaft I3 outwardly adjacent the bearing I5 is a collar or flange I'I. The shaft I3 extends outwardly from the housing I| and is formed at its outwardly extending portion with a longitudinal keyway I8. Designated at I9 is a sleeve member which fits slidably over the outer end portion of the shaft I3 and is formed with an integral, longitudinal key `2l! which is slidably received in the keyway I8. The sleeve member I9 extends rotatably through a bushing 2| which is threaded into the end wall of the housing II, as shown at 22, the sleeve member I9 being formed with an end annular flange 23. Designated at 24 is a coil spring which encircles the shaft I3 and bears at one end on the collar I'I, and at the other end on the Hansje 23, biasing the sleeve memberl9 one wardlv te a position wherein the flange 23 abuis the inner rim of the bushing 2l,- Desisnated at 25 is a disc member carried on the end of the sleeve member I9, said disc member being, for example, a sanding disc, a bufng disc,l a polishing wheel, or any other desired tool.

Secured in the compartment of the housing designated at 26, as viewed in Figure l, is a sup.- porting member 2l'. of insulation material, said supporting member extending at right angles to the shaft I3, and secured on said supporting member are the respective contact members 28 and 29. The contact member 29 comprises a resilient arm which is provided at its end with a contact element 3U, the contact member 28 being provided with a similar contact element 3|. When the iiange 23 is in abutment with the inner edge of the bushing 2|, as shown in Figure 1, the contact elementspSI) and 3| are in separated positions. The flange 23 has secured to its outer surface an annular rim 32 of insulation material which is adapted to engage the contact arm 29 responsive to movement of the sleeve member inwardly with respect to housing I I, engagement of the rim 32 with the contact arm 29 being sufficient to flex the contact arm 29 counterclockwise, as viewed in Figure 1, forcing the contact member 30 into engagement with the contact member 3|. This action occurs when the tool element 25 is pressed against the surface to be engaged by the tool element, as for example, the surface of a floor to be sanded, or a surface to be polished. The contacts 39 and 3| are connected in series with the energizing circuit of the motor I2, whereby the motor I2 becomes energized as soon as the aforesaid contact elements 30 and 3| are engaged with each other. Therefore, in operating the device, the motor I2 is normally de-energized, but as soon as the tool element 25 is pressed against the surface to be polished, sanded, or the like, the motor becomes energized and the operation of the tool commences. As soon as pressure is released on the tool element 25, the spring 214 forces the flange 23 into abutment with the inner edge of the bushing 2|, namely, to the position shown in Figure l, thereby releasing the flexible contact arm 29 and opening the motorenergizing circuit.

The surface of the insulating bead 32 is preferably smoothly rounded and highly polished, and said bead element is made of material having a high resistance to abrasion, whereby the Kbead 32 may rotate relative to the contact element 29 without undue Wear thereof.

When it is desired to change the type of tool element driven by the device, the bushing 2| is unscrewed, allowing the sleeve member I9 and said bushing to be removed and to be replaced by the bushing associated with the sleeve element of the new tool element to be employed with the device.

While a specific embodiment of an improved electrical tool of the motor-driven type has been disclosed in the foregoing description, it will be understood that Various modications within the spirit of the invention may occur to those skilled in the art. Therefore, it is intended that no limitations be placed on the invention except as defined by the scope of the appended claim.

What is claimed is:

An electrical tool of the character described comprising a housing, an electric motor mounted inside said housing, a tool member, a sleeve element carried by said tool member and being slidably and non-rotatably engaged on the motor shaft and extending outside the housing, spring means biasing said tool member outwardly relative to the housing, a stationary switch contact mounted in said housing and extending substantially parallel to said shaft, a exible switch contact mounted in said housing inwardly adjacent to said stationary contact and being bendable into engagement with said stationary switch contact, said flexible switch contact being normally parallel to and disengaged from said stationary switch contact, an annular flange on said sleeve element having a radius greater than the distance of said exible contact from the axis of the shaft and having a rounded outer rim which is normally spaced axially outwardly from said flexible contact and is engageable with said flexible switch contact to move the flexible contact radially outwardly into engagement with the stationary contact responsive to inward axial movement of the tool member relative to the housing, and a normally open energizing circuit connected to said motor and including said contacts in series therewith and being arranged to be closed responsive to the closure of said contacts.

KENNETH D. BURRELL. RICHARD C'. LATSON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,449,908 Guckin et al Mar. 27, 1923 1,528,628 Powell Mar. 3, 1925 1,624,758 Powell et al Apr. 12, 1927 1,723,009 Brackett Aug. 6, 1929 1,941,823 Bohland Jan. 2, 1934 2,094,549 Miller Sept. 28, 1937 2,355,852 Fisher Aug. 15, 1944 2,431,316 Dudley et al. Nov. 25, 1947 

